Private Keys and Seed Phrases

Private keys authorize

A private key produces signatures that satisfy spending conditions. Anyone who obtains it can usually move the associated funds; no support desk can cancel a valid Bitcoin signature.

Seeds simplify backup

Modern wallets often derive many private keys from one human-readable recovery phrase. The phrase is therefore a master backup, not a password to type into websites or share for technical support.

Name who controls the key. A wallet interface, an exchange account, and a recovery backup can expose different people to different failures.

Backup against realistic loss

Protect against theft, fire, water, accidental disposal and forgotten instructions. Store offline, verify legibility and ensure trusted heirs can follow a carefully designed recovery plan without creating an easy path for an attacker.

From one secret to every address

A private key is a 256-bit number. From it, elliptic-curve mathematics derives a public key, and hashing the public key produces an address. The operation runs one way: anyone can check that a signature matches a public key, and nobody can recover the private key from either. Modern wallets do not store keys individually.

They start from a single random seed, encode it as a recovery phrase, and derive a tree of keys from it deterministically, so one backup covers every address the wallet will ever generate. That is what 'hierarchical deterministic' means on a wallet's feature list.

The 2,048 words and what they encode

A recovery phrase is the seed written in a form humans can copy. The standard wordlist has 2,048 entries, each chosen so its first four letters are unique and no two words are confusingly similar. Twelve words encode 128 bits of entropy plus a checksum; twenty-four words encode 256 bits.

The last word is partly a checksum, so a phrase with one wrong word is usually rejected rather than silently opening an empty wallet. An optional passphrase can be added on top; it is not stored anywhere, and a different passphrase yields a different, empty wallet with no error.

Storage that survives the realistic threats

The threats are fire, flood, theft, a house move, your own forgetfulness and your heirs' ignorance — not cryptanalysis. Paper in a fireproof box covers most of them; a stamped metal plate covers the rest, and for anything larger than pocket money the phrase should belong to a hardware wallet rather than a phone. Keep two copies in different places.

Do not split a single phrase into halves stored separately, which halves an attacker's work while doubling your chance of losing one part; use a proper multisig or a Shamir scheme if you need that property. Tell one trusted person where the backup is and what it is for. And never type the words into anything connected to the internet.

Turn this into a recovery check

Write down who can authorize a spend, what must be backed up, and how recovery will be tested without exposing a seed phrase. Start with a small amount before relying on a new custody setup.